In multiple-part tool holding arrangements for machine tools with provisions for automatic tool changing, the problem arises that upon tool changing, the connection part carrying the tool must be tightened with a high degree of concentricity against the receiver body that is connected to the machine tool spindle. To this end, holding arrangements have become known in practice, in which the centering stub of the connection part is embodied as a cylinder and can be pushed into a cylindrical receiving bore, of close tolerances, in the receiver body, until plane surfaces provided on the respective end faces of the connection part and the receiver body come into engagement with one another. Although it is possible for the forces exerted at right angles to the axis of rotation (that arise during chip-producing machining) to be absorbed via these plane surfaces resting on one another, still the degree of concentricity that is attainable is limited, because of the machining tolerances of the cylindrical surfaces of the centering stub and of the receiving bore. The connection between the receiver body and the connection part is also vulnerable to tilting when the two parts are joined. If the centering stub is not aligned precisely coaxially with the receiving bore, then damage occurs to the centering stub or the receiving bore, impairing concentricity or even making it difficult or impossible to release the connection between the two parts. In order to facilitate joining, the centering stub and the receiving bore have in the prior art already been embodied in stepped fashion.
In other known holding arrangements, a conical connection between the connection part and the receiver body has been used, in accordance with customary industrial standards, such as standard tapers. The cone angle tolerances are designed such that the outer conical surface of the centering stub in any case bars the load at its maximum diameter, so as to attain maximum stability of the connection. In applications in which very strong forces are exerted upon the connection part at right angles to the axis of rotation, however, it is no longer possible for the cooperating conical surfaces alone to absorb such forces with sufficient stability.
Therefore if relatively strong lateral forces must be expected, then in addition the receiver body and the connection part must be provided with accurately ground plane surfaces extending at right angles to the axis of rotation, which upon the joining of the two parts are tightened by the tightening or holding device so that they rest on one another. However, in order to attain a connection between two parts that involves a receiving cone and a planar surface, the most stringent possible accuracy in machining is required, because the connection is overdefined. If the outer cone surface of the centering stub and the inner cone surface of the receiving bore are realized such that one fits precisely inside the other, then a gap will still remain between the two plane surfaces; alternatively, if the two plane surfaces are intended to rest exactly against one another, then a certain amount of air must be present between the outer and inner cone surfaces.